Higher: redox, strong and weak acids

The idea

Oxidation is loss of electrons and reduction is gain of electrons (OIL RIG). In displacement reactions, the more reactive metal is oxidised. Strong acids (hydrochloric, nitric, sulfuric) are completely ionised in water; weak acids (ethanoic, citric, carbonic) are only partially ionised. For a given concentration, a stronger acid has a lower pH. When the H⁺ concentration increases by a factor of 10, the pH falls by 1. At electrodes: cathode 2H⁺ + 2e⁻ → H₂; anode 4OH⁻ → O₂ + 2H₂O + 4e⁻.

1. Use OIL RIG for electrons.
2. Separate strength (ionisation) from concentration (amount per volume).
3. Use the factor of 10 rule for pH.

Watch out A concentrated weak acid is not the same as a strong acid: strength is about ionisation.